Fapon's Innovative Double Antibody VD Reagent Solution: Enhancing Vitamin D Diagnostics

Vitamin D (VD) is an essential fat-soluble vitamin that has been shown to reduce levels of cytokines (inflammatory proteins) by binding to receptors _[1] . Adequate levels of vitamin D also protect against respiratory infections _[2] . Vitamin D deficiency, excess or abnormal metabolism can affect the absorption of calcium and phosphorus in the human intestine and bone metabolism _[3] .

Low levels of vitamin D can increase the risk of cardiovascular disease by activating the proinflammatory cascade, leading to endothelial dysfunction and increased arterial wall stiffness _[4] . In addition, vitamin D is easily stored in the body (mainly in the liver), which may lead to adverse reactions in excess _[5] . It is evident that accurate vitamin D test results can help to accurately assess the nutritional status, malabsorption or toxicity level of human vitamin D in clinical settings.

Vitamin D test

In 2011, an expert group led by Professor Holick MF, an internationally renowned expert in vitamin D research, authored the Clinical Practice Guidelines for the Evaluation, Prevention and Treatment of Vitamin D Deficiency for JCEM, a clinical academic journal of the American Society of endocrine. In general, 25-hydroxy vitamin D (25 (OH) D) concentrations below 20 ng/mL (50 nmol/L) are referred to as vitamin D deficiency, and screening is recommended for people who may be at risk for vitamin D deficiency.

The Expert Consensus on the Clinical Application of Vitamin A and Vitamin D in Children in China, which was discussed and formulated by the expert group of the child care Branch of the Chinese Preventive Medical Association in 2021, clearly defined the criteria and criteria for determining vitamin D deficiency, and emphasized that serum 25 (OH) D concentration ≥ 50 nmol/L (20 ng/mL) was normal. The prevalence of vitamin D deficiency and deficiency among children aged 3-5 years in China is about 51.9%, which is slightly higher in urban areas than in rural areas.

Vitamin D detection method

Currently, due to the standardization of vitamin D detection has just started, there are obvious differences in the results of various detection methods, especially commercial methods and the self-built methods of different laboratories.

As the gold standard of small molecule detection, LC-MS/MS has good specificity and high accuracy, but its throughput is low, preprocessing is complex, equipment and personnel requirements are high, and most importantly, the report time is more than 6 hours, making it difficult to provide same-day reporting and limiting its widespread use.

Currently, the detection of vitamin D by mainstream chemiluminescence manufacturers is basically competitive, and the negative and positive consistency with the gold standard LC-MS/MS is poor. The main reason may be that when the sample contains 25-OH-VD 2 , the correlation between competition method and LC-MS/MS test results decreases.

The double antibody sandwich method is a reagent excess detection method, which has obvious advantages in sensitivity, specificity and detection range compared with the competition method. In recent years, the small molecule sandwich method for vitamin D detection has gained increasing recognition by manufacturers and clinicians.

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Vitamin D biochemistry platform detection

The Biochemistry testing platform is a necessary testing platform for hospitals at all levels, with a very wide range of coverage on the instrument. The biochemical VD reagent combines the dissociation reagent with the R1 reagent to achieve the detection with double reagent components, which has the characteristics of no sample pretreatment, low sample size (only 3 μL), high automation of operation and short TAT time. Compared with ELISA, LC-MS/MS and other platforms, the biochemistry detection platform has obvious advantages in terms of operation convenience, instrument familiarity and package richness.

biochemistry platform supports blood calcium, blood phosphorus, bone alkaline phosphatase and other bone testing items, as well as a wealth of liver and kidney function testing packages, can help clinical achieve more accurate disease positioning.

(Figure: Pathogenesis of vitamin D deficiency rickets.)

Fapon Launches Double Antibody VD Reagent Solution of Biochemistry Platform

[Methodology]: Latex immunoturbidimetry and double antibody method

[Reagent Formulation]: Liquid double reagent, suitable for all brands of automatic biochemical analyzers, convenient and fast detection

[Reagent performance]: Each performance index is good, meeting the testing requirements of each laboratory.

1. The sensitivity is high, the lowest detection limit is less than or equal to 2ng/mL, and the analytical sensitivity reaches 4ng/mL.

   
   

2. Strong stability, both reagents and liquid calibrators show excellent stability

   Reagent Accelerated Stability Test Data

   
   

   Liquid Calibrator Accelerated Stability Test Data

   
   

3. Compared with the turbidimetric reagent of manufacturer D, it showed high correlation in the full range (142 samples, the measured values were evenly distributed between 4.5-78.1 ng/mL, the samples were not excluded, the data were not modified, R² > 0.96).

   
   

4. Compared with the chemiluminescent VD detection system of manufacturer B, it showed a high correlation (40 clinical samples, the measured values were evenly distributed between 5.8 and 146.1 nmol/mL, the samples were not excluded, the data were not modified, R² > 0.91).

   
   

5. Comparison with LC-MS/MS detection platform (instrument model: Waters UPLC/Xevo TQ-S) showed good correlation (40 clinical samples, the measured values were evenly distributed between 5.8-146.1 nmol/mL, the samples were not excluded, the data were not modified, R² > 0.83).

   
   

6. Linearity range is 4-150ng/mL, Hook is higher than 400ng/mL

   
   

Fapon’s Double Antibody VD Reagent Solution Product Information

References

[1] Lang, Pierre Olivier , and  D. Samaras . "Aging Adults and Seasonal Influenza: Does the Vitamin D Status (H)Arm the Body?." Journal of aging research 2012(2012):806198.

[2] Martineau, Adrian R , et al. "Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data." BMJ 356(2017):i6583.

[3] Osteoporosis and Bone Mineral Disease Branch of Chinese Medical Association. "" Clinical application consensus of vitamin D and its analogues. "" Chinese Journal of endocrine and Metabolism 34.3 (2018): 14.

[4] Qin Jianhua, and Wang Li. "Research progress on the relationship between vitamin D deficiency and cardiovascular disease risk factors." Chinese Journal of Clinical Physicians: Electronic Edition 2 (2016): 5.

[5] Laboratory Medicine Branch of Chinese Geriatric Health Care Medical Research Association, Laboratory Medicine Branch of Chinese Geriatric Medical Association. Expert consensus on standardization of 25-hydroxyvitamin D detection by liquid chromatography-tandem mass spectrometry [J]. Chinese Journal of Laboratory Medicine, 2021, 44 (7): 587-595.

[6] Kimmie Ng, et al., (2019). Supplementation on Progression-Free Survival Among Patients With Advanced or Metastatic Colorectal Cancer. JAMA, 10.1001/jama.2019.2402